Rigol DS2000 series oscilloscope repair

My Rigol DS2072A-S suddenly stopped working. Fortunately the problem in this case was relatively easy to find and simple to fix.
Power and FGBoard pinouts: www.eevblog.com/forum/testgea...
INDEX
0:00 Index
0:10 Introduction: My Rigol DS2072A-S oscilloscope has died!
0:43 Opening the scope
1:56 Testing the power supply off-load
2:36 Plan of attack
3:18 Removed the signal generator board - now it boots!
4:07 Mapping out the signal generator power supplies
4:42 Fault found!
6:03 Capacitor replaced, still not working
6:20 Capacitor had failed straight away, let's try another
6:40 We're back in business!

[@fredflintstone1]

very handy video shows what volatages should be seen and hopefully the correct value of the SMD Capacitor:-) Glad you found the problem

[@AintBigAintClever]

You're glad? I thought I was going to have to drag my old 20MHz Hameg down from the attic ahead of buying a new scope :D I couldn't find any pinout info but it's now on EEVblog. Working it all out definitely helped troubleshoot the function generator board, without the pinout it just looked like it had an extra ground pin.

[@SeanBZA]

I guess there was a turn on spike that killed the capacitor, and the next one, probably from a LC filter on the 7V5 rail. Probably the capacitor on the main board itself is open circuit, or the power supply has a failing capacitor on the 5V rail, likely the rail used for regulation feedback, that allows it to generate a brief period of overvoltage on start up. Best to open the PSU case and check the secondary side capacitors, along with all small low value low voltage electrolytics on the primary side. Primary side best to check by replacing, as heating them up during desoldering will temporarily make them appear good enough, if they are marginal. Use good quality 105C ones, the originals are likely cheap brands, and 7 years is likely EOL for them already. Main filter caps really only need replacing if bulging, they normally run well under the ripple current rating, but the small ones, and secondary ones, really do run at or past ratings.

[@AintBigAintClever]

Would scoping the secondary voltages for ripple show up any duff ones? Remember that although this unit's 7 years old, it's not been running for 7 years. 24 hours is a more likely scenario.

[@SeanBZA]

@@AintBigAintClever Yes it would, but remember those cheap caps are likely only rated for 1000 hours on the optimistic side, and 7 years is 56k hours, so likely they are either at end of life, or pretty close to it. I have seen plenty of new capacitors that have been in storage for a few years that simply fail on power on, because they degraded in storage. If it is from the 1960's or 70's on a old iron core power supply they are fine, just a little more ripple, but any one with a 105C rating has a definite shelf life.

[@RambozoClown]

@@AintBigAintClever Well for that you would need a scope. Catch 22. Maybe you will be making a trip to the attic.

[@AintBigAintClever]

​@@RambozoClown That's like the catch 22 of Antex soldering irons, or at least the ones I've got. If the element fails you can replace it, but the element wires are soldered inside the handle, so you need another iron. if the scope starts misbehaving or I run out of things to do, the old Hameg's coming out to play.

[@iamdarkyoshi]

Very interesting faultfinding. At least it was on the daughterboard and was easy to spot! Side note, what's the outro song? Sounds like an amiga modtracker song

[@AintBigAintClever]

That's exactly what it is :) janeway.exotica.org.uk/release.php?id=3545

[@RambozoClown]

If you hadn't nailed that cap, it'd be pushing up the daisies.

[@martinkuliza]

I think it's pretty said that we live in a world where , on an 8min video you need to say don't want to watch the entire video... then put up a menu to skip to i'ts not like it's a 2 hour video, i think if a person needs this for 8mins of video they shouldn't be in electronics

[@AintBigAintClever]

Anything more than a couple of minutes and I put an index on. Been doing it long before KZbin made it a thing and let you carve up the navigation slider.

[@martinkuliza]

@@AintBigAintClever Yeah i understand Unfortunately you tube is not an electronics buff and doesn't understand people like us, You tube caters for LAZY PEOPLE LOL let there be no bullshit about it And i understand this is your business and you have to do what you have to do